1. Field of the Invention
The present invention relates to a piercing terminal penetratingly connected to a flexible flat circuit body, in which the periphery of flat conductor portion is covered with a coating consisting of an insulator, such as a flexible print circuit (FPC) and flexible flat cable (FFC).
The present invention also relates to a machine and method for crimping a piercing terminal, by which the piercing terminal having a claw piece for piercing is crimp-connected to the flexible flat circuit body.
2. Description of the Related Art
An example of the art relating to such a piercing terminal and method for crimping a piercing terminal is described in Japanese Patent Publication No. S57-48833.
As shown in FIGS. 11 and 12, a piercing terminal 40 includes a crimp-connection part 43 having an approximately flat basal plate 41 and claw pieces 42 arising from both sides of the basal plate 41. Each claw piece 42 consists of a wide base 42a joining to the basal plate 41 and a narrow free end 42b continuing to the base 42a. 
A flat circuit body 46 (see FIG. 12) being connected to the crimp-connection part 43 is a flexible circuit body, in which the periphery of a band-shaped conductor portion 47 is covered with a coating 48 consisting of an insulator, and is a thin circuit body called FPC or FFC.
The claw piece 42 adjoining each other in the length direction of the piercing terminal 40 is parted away from each other forming a tapered space therebetween. The base side of the claw piece 42 continues to the basal plate 41 and the joining portion of the claw pieces 42.
Since the claw piece 42 provided at both sides of the width direction of the basal plate 41 is alternately formed with each other, therefore at the opposite side of each claw piece 42 in the width direction, there is a tapered-shape space facing thereto. The claw piece 42 includes a round-shaped end 42c and a sharp side edge 42d. 
At the center of the basal plate 41, there is provided a protrusively striped contact portion 44. In the direction crossing the contact portion 44 at right angles, there is formed a groove 45, which extends up to the inner surface of the claw piece 42.
As shown in FIG. 12, the claw piece 42 pierces through the conductor 47, thereby the piercing terminal 40 is fixed to the flat circuit body 46. The free end 42b of the claw piece 42 is caulked inwardly along a press surface 49a of a crimper 49 and stripes the coating 48 of the flat circuit body 46 away so as to come in contact with the conductor 47, thereby the electric conduction is attained.
However, the conventional piercing terminal described above has the following problems to be solved.
One problem is that since the piercing terminal 40 has a plurality of claw pieces 42, when the flat circuit body 46 becomes thick, the claw piece 42 might not be able to pierce through the flat circuit body 46. To the contrary, if the number of the claw pieces 42 is reduced, the connection between the piercing terminal 40 and the flat circuit body 46 might become insufficient, resulting in that the piercing terminal 40 might come off from the flat circuit body 46.
Another problem is that when the thickness of the conductor 47 becomes different, a plurality of the piercing terminals 40 having different size must be prepared. That is, when the piercing terminal 40 is crimped between an anvil (not shown in the figure) and crimper 49, the piercing terminal 40 forms a crimp height depending on the shape of the crimper 49. If the flat circuit body 46 or conductor 47 is thin, the end of the claw piece 42 does not reach the conductor 47, the connection between the piercing terminal 40 and the flat circuit body 46 might become insufficient. To the contrary, if the flat circuit body 46 or conductor 47 is thick, the protrusion length of the claw piece 42 becomes short, resulting in that the claw piece 42 might not be caulked in a curled shape.
In such a case described above, a piercing terminal having a suitable size must be selected and therefore, the number of parts increases causing the cost up and the parts control becomes complicated causing the deterioration in workability.
Another problem is that the contact area between the flat circuit body 46 and the claw piece 42, which depends on the caulked shape of the claw piece 42, is small. That is, since the radius of curvature of the caulked portion of the claw piece 42 is small, the contact area between the conductor 47 and the claw piece 42 is small, therefore a good electric conduction cannot be attained. That is, when the crimper 49 caulks the claw piece 42, if a fabrication error takes place, a good electric conduction might not be attained.
FIGS. 13A and 13B are cross sectional views before and after crimping, respectively, illustrating an example of a conventional method of crimping a piercing terminal.
A piercing terminal 240 and a flat circuit body 246 are sandwiched between a crimper 244, which is a die for pressing, and an anvil 245, which is a die as a pedestal, and caulked into each other so as to be crimped.
The anvil 245 is a pedestal, on which the piercing terminal 240 is placed, and there is formed a projection 245a having a trapezoid shape in its cross section on the center of the anvil 245. The projection 245a fits to the bottom of a protrusively striped contact portion 241a of the piercing terminal 240.
The crimper 244 is provided with a pair of curved portions 244a, each of which is parted away from the other by a protrusion 244b having a flat part. The protrusion 244b faces the projection 245a and is set to be movable relatively to the anvil 245.
However, the conventional method of crimping a piercing terminal described above has the following problems to be solved.
One problem is that the contact area between the flat circuit body 246 and the claw piece 242 of the piercing terminal 240, which depends on the caulked shape of the claw piece 242, is small. That is, the claw piece 242 is caulked inwardly along the curved portion 244a of the crimper 244 and since the radius of curvature of the bent portion of the claw piece 242 is small, if the thickness of the conductor 247 of the flat circuit body 246 becomes different, the contact area between the claw piece 242 and the conductor 247 becomes decreased or increased, therefore a good electric conduction might not be attained. Particularly, in case of an electric wire of an electric power system, since the electric wire supplies power from a battery to loads and a large current flows in the wire in comparison with a wire of a signal system, an electric resistance becomes large when the contact area is small, resulting in bad electric conduction.
In such a case, in order to adjust a crimp height of the piercing terminal 240, a distance between the crimper 244 and anvil 245 must be changed and otherwise the piercing terminal 240 having a different size must be prepared, resulting in that the parts control becomes complicated causing the deterioration in workability.
It is therefore an objective of the present invention to solve the above problems and to provide a piercing terminal having high reliability for crimping, by which the piercing terminal can be securely pierced through a flat circuit body even if the flat circuit body has a thick conductor and the piercing terminal has a plurality of claw pieces.
It is also an objective of the present invention to provide a highly reliable machine and method for crimping a piercing terminal, by which the piercing terminal can be securely crimp-connected to a flat circuit body having different thickness.
In order to attain the above objective, the present invention is to provide a piercing terminal to be connected to a flat circuit body comprising:
an electrically conductive basal plate; and
a plurality of claw pieces arising from both sides in the width direction of the basal plate, wherein a protrusion height of each claw piece is different from that of the other claw piece.
With the construction described above, each claw piece pierces through the flat circuit body in sequence of their height and shearing force per claw piece becomes large even when there are a plurality of claw pieces, thereby the claw pieces securely pierce through the flat circuit body.
The present invention is to provide a piercing terminal to be connected to a flat circuit body comprising:
an electrically conductive basal plate; and
a plurality of claw pieces arising from both sides in the width direction of the basal plate, wherein each of a pair of claw pieces has the same protrusion height and a protrusion height of each pair of claw pieces is different from that of the other pair of claw pieces.
With the construction described above, a pair of claw pieces simultaneously pierces through the flat circuit body, thereby the piercing can be carried out in a good balance.
Preferably, a notch is formed between the claw pieces adjoining each other in the length direction of the basal plate.
With the construction described above, the claw piece pierces through the flat circuit body up to the root thereof and the contact area between the claw piece and flat circuit body increases, thereby preventing defective joining from occurring.
Preferably, a plurality of the claw pieces are formed so that an imaginary line connecting the tops of the claw pieces gradually inclines as approaching an end in the length direction of the basal plate.
With the construction described above, each claw piece pierces through the flat circuit body in sequence of their height and since a crimper presses the end of the claw piece protruding from the flat circuit body, the claw piece is caulked in a curled-shape, thereby the flat circuit body is firmly held between the end of the claw piece and the basal plate of the piercing terminal.
The present invention is to provide a piercing terminal to be connected to a flat circuit body comprising:
an electrically conductive basal plate; and
a plurality of pairs of claw pieces arising from both sides in the width direction of the basal plate, wherein a distance between a pair of claw pieces is different from that between the other pair of claw pieces.
With the construction described above, even if the flat circuit body has the conductor having a different width, at least one of the pairs of claw pieces electrically connects to the conductor, thereby preventing defective conduction from occurring. Further, there is no need to prepare a plurality of piercing terminals in response to the width of the conductor, thereby the number of the parts decreases and the cost can be reduced.
Preferably, each pair of claw pieces is arranged in a tapered shape in the length direction of the basal plate.
With the construction described above, the claw piece can securely and easily catches the flat circuit body and never comes off from the flat circuit body even when the flat circuit body is accidentally pulled in its length direction, thereby the holding power for holding the flat circuit body of the claw piece is improved.
Preferably, at least one pair of claw pieces is alternately formed.
With the construction described above, when the claw piece situated at both sides in the width direction of the flat circuit body is caulked in a curled-shape, the flat circuit body having the conductor of small width can be caulked without interference between the claw pieces at both sides. Therefore, even in a case of the flat circuit body having small width such as an electric wire of a signal system, a secure electric contact can be attained.
Preferably, a notch is formed between the claw pieces adjoining each other in the length direction of the basal plate.
With the construction described above, the claw piece pierces through the flat circuit body up to the root thereof and the contact area between the claw piece and flat circuit body increases, thereby preventing defective joining from occurring.
Preferably, a protrusion height of each pair of claw pieces is different from that of the other pair of claw pieces.
With the construction described above, each claw piece pierces through the flat circuit body in sequence of their height and shearing force per claw piece becomes large even when there are a plurality of claw pieces, thereby the claw pieces securely pierce through the flat circuit body.
The present invention is also to provide a machine for crimp-connecting a piercing terminal into a flat circuit body having a flat conductor, the piercing terminal including a plurality of claw pieces piercing through the flat circuit body, comprising:
a crimper for pressing; and
an anvil as a pedestal facing the crimper, wherein the crimper is provided with a caulking portion facing the anvil, the caulking portion is provided with a pair of depressions each of which having a depressed curved surface and a protrusion having a protrusive curved surface situated between the pair of depressions, the boundary between the pair of depressions and the protrusion is linked with a smooth curved surface, and the caulking portion caulks the claw pieces of the piercing terminal.
With the construction described above, the claw piece of the piercing terminal protruding from the flat circuit body comes in surface contact with the flat circuit body along the conductor of the flat circuit body.
The present invention is also to provide a method of crimp-connecting a piercing terminal into a flat circuit body having a flat conductor, the piercing terminal including an electrically conductive basal plate and at least a pair of claw pieces arising from both sides of the basal plate, comprising the steps of:
sandwiching the flat circuit body and piercing terminal between a crimper for pressing and an anvil as a pedestal;
piercing the pair of claw pieces through the flat circuit body; and
caulking the pair of claw pieces in a curled shape, wherein the pair of claw pieces protruding from the flat circuit body is inwardly curved imitating a depression of a caulking portion of the crimper and thereafter the pair of claw pieces is curved in the opposite direction of the inwardly curved direction imitating a protrusion of the caulking portion.
With the construction described above, the end of each claw piece is caulked along the conductor of the flat circuit body, and the approaching direction between the crimper and anvil becomes the same with the direction, in which the end of the claw piece presses the flat circuit body, thereby the piercing terminal firmly joins with the flat circuit body.
Preferably, when the pair of claw pieces is caulked with the crimper and anvil, a gap is formed between the flat circuit body and the protrusion of the crimper, thereby an end of the claw piece is advanced into the gap.
With the construction described above, the end of the claw piece is sandwiched and presses between the crimper and the flat circuit body, therefore the contact area between the claw piece and the flat circuit body increases, thereby preventing defective joining and defective conduction from occurring.